Quite a bit is possible with this firmware. What's the difference between those modes and how does your VOIP know? In otherwords what is the flag or data its looking for? This "feels" like one of those things they may actually not be too hard and yet by offering it will move Tomato more and more into the "most user friendly" category than it already is.

Its also this kind of thing that improves the firmware but yet does not take cpu cycles to do so. Or at least not that many.